Driving equipment for synchronous motors

Abstract

Providing control apparatus with a maximum torque/current ratio control means by which the relationship between the maximum torque and current amplitudes and the relationship between the maximum torque and current phases are converted to numeric expressions including one or more than one linear function with the torque taken as the parameter, then the current amplitude command and current phase command data that yields a maximum torque is computed, and computed data is sent as an output signal.

What is claimed is:  
     
       1. A driving equipment for a synchronous motor, comprising: 
       an inverter for converting a direct-current voltage to an alternating current or a direct current and supplying the current to said synchronous motor;  
       a control apparatus for controlling the output voltage and frequency of said inverter; and  
       a means for detecting or estimating the rotational speed of said synchronous motors; wherein  
       said control apparatus is further equipped with a means for issuing a torque command that matches the rotational speed and a rotational speed command, and a means for receiving the torque command (T*) as an input signal, computing a current amplitude command (I*) and current phase command (φ*), and sending the commands as output signals;  
       said receiving, computing and sending means performs the computation of the current amplitude command (I*), and current phase command (φ*) according to the following first and second linear functions using the torque command (T*) as a parameter;  
       
         
           
             I*=A·T*+B  
           
         
       
       
         
           φ*= F·T*+G;  and  
         
       
       A, B, F and G are constants determined for the synchronous motors to maximize achievable torque with a minimum current.  
     
     
       2. A driving equipment for a synchronous motor, according to  claim 1 , wherein: 
       said receiving, computing and sending means uses a third linear function for computing the current amplitude command (I*) which passes the origin of I-T coordinate in combination with the first linear function;  
       said third linear function is defined by the expression  
       
         
             I*=C·T* ; and  
         
       
       C is a constant determined in connection with the concerned synchronous motor.  
     
     
       3. A driving equipment for a synchronous motor according to  claim 1 , wherein; 
       said receiving, computing and sending means uses a fourth linear function for computing the current phase command (φ*) which passes the origin of φ-T coordinate, in combination with the second linear function;  
       said fourth linear function is defined by the expression,  
       
         
           φ*= H·T*;  and  
         
       
       H is a constant determined in connection with the concerned synchronous motor.  
     
     
       4. A driving equipment for a synchronous reluctance motor, comprising: 
       an inverter for converting a direct-current voltage to an alternating current or a direct current and supplying the current to said synchronous reluctance motors, in which a plurality of annular magnetic paths are formed by providing multilayer slits in a core of the motor rotor;  
       a control apparatus for controlling the output voltage and frequency of said inverter; and  
       means for detecting or estimating the rotational speed of said synchronous reluctance motor; wherein  
       said control apparatus is further equipped with a means for issuing a torque command that matches the rotational speed and a rotational speed command, and a means for receiving the torque command (T*) as an input signal, computing a current amplitude command (I*) and a current phase command (φ*), and sending the commands as output signals;  
       said receiving, computing and sending means performs the computation of the current amplitude command (I*) and current phase command (φ*) according to the following first (1) and second (2) linear functions is using the torque command (T*) as a parameter;  
       
         
           
             I*=A·T*+B  
           
         
       
       
         
           φ*= F·T*+G;  and  
         
       
       A, B, F and G are constants determined for the synchronous reluctance motor.  
     
     
       5. A driving equipment for a synchronous reluctance motor according to  claim 4 , wherein: 
       said receiving, computing and sending means uses a third linear function for computing the current amplitude command (I*) which passes the origin of I-T coordinate in combination with the first linear function;  
       said third linear function is defined by the expression  
       
         
             I*=C·T*;  and  
         
       
       C is a constant determined for the synchronous reluctance motor.  
     
     
       6. A driving equipment for a synchronous reluctance motor according to  claim 4 , wherein: 
       said receiving, computing and sending means uses a fourth linear function for computing current phase command (φ*) which passes the origin of φ-T coordinate in combination with the second linear function;  
       said fourth linear function is defined by the expression  
       
         
           φ*= H·T*;  and  
         
       
       H is a constant determined in connection with the concerned synchronous reluctance motor.